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FW: [F&O May 2] distinct-values

From: Ashok Malhotra <ashokma@microsoft.com>
Date: Fri, 30 May 2003 07:41:54 -0700
Message-ID: <E5B814702B65CB4DA51644580E4853FB0891E199@red-msg-12.redmond.corp.microsoft.com>
To: <public-qt-comments@w3.org>

Resending.  Failed to appear in the archive.

All the best, Ashok

> -----Original Message-----
> From: Ashok Malhotra
> Sent: Thursday, May 29, 2003 4:53 AM
> To: 'Michael Brundage'; public-qt-comments@w3.org
> Subject: RE: [F&O May 2] distinct-values
> 
> Michael:
> The current definition of fn:distinct-values does not require a total
> order.  Please take a look.
> 
> 15.1.11 fn:distinct-values
> fn:distinct-values($arg as xdt:anyAtomicType*) as xdt:anyAtomicType*
> fn:distinct-values( $arg  as xdt:anyAtomicType*,
> $collationLiteral  as xs:string) as xdt:anyAtomicType*
> 
> Returns the sequence that results from removing from $arg all but one
of a
> set of values that are eq to one other. All the values must be of a
single
> type or one if its subtypes (for numeric values, the numeric promotion
> rules defined in 6.2 Operators on Numeric Values are used to promote
all
> values to a single common type). The type returned is a sequence of
values
> of the same type as $arg. Equality must be defined for the type. If
this
> condition is not satisfied, an error is raised ("Type does not have
> equality defined"). For detailed semantics see section 6.2.2 of
[XQuery
> 1.0 and XPath 2.0 Formal Semantics].
> 
> The collation used by the invocation of this function is determined
> according to the rules in 7.3 Equality and Comparison of Strings.
> 
> If $collationLiteral does not represent a valid collation, an error is
> raised ("Invalid collation argument to fn:distinct-values()").
> 
> If $arg is the empty sequence, the empty sequence is returned.
> 
> For xs:float and xs:double values, NaN is considered to be equal to
itself
> and 0.0 is equal to -0.0.
> 
> If an xs:dateTime, xs:date or xs:time value does not have a timezone,
an
> implicit timezone is provided by the evaluation context. The
normalized
> value is adjusted using this implicit timezone if necessary. The
adjusted
> normalized value is used to compute distinctness. If multiple adjusted
> normalized values compare equal but the accompanying timezones are
> different, it is *implementation dependent* which value is returned.
> 
> Equality of string values is determined according to the collation
that is
> used. Which value of a set of values that compare equal is returned as
> well as the order in which values returned is *implementation
dependent*.
> If the type of the items in $arg is not xs:string and
$collationLiteral is
> specified, the collation is ignored.
> 
> 
> 
> All the best, Ashok
> > -----Original Message-----
> > From: Michael Brundage [mailto:xquery@attbi.com]
> > Sent: Wednesday, May 28, 2003 6:44 PM
> > To: public-qt-comments@w3.org; Ashok Malhotra
> > Subject: [F&O May 2] distinct-values
> >
> > The distinct-values function requires that the type be totally
ordered -
> -
> > why?  It only needs equality.
> >
> > Also, the current definition allowing subtypes means that not only
is
> the
> > order of the result implementation-dependent, but so is the
(dynamic)
> type
> > and contents of the result.  For example,
> >
> > distinct-values(1, 1.0) => 1 or 1.0 (implementation-dependent)
> > distinct-values("x", xs:token("x")) => "x" or xs:token("x")
> > (implementation-dependent)
> >
> > Etc.
> >
> >
> >
> > Michael Brundage
> > Writing as
> > Author, "XQuery: The XML Query Language" (Addison-Wesley, to appear
> 2003)
> > Co-author, "Professional XML Databases" (Wrox Press, 2000)
> >
> > not as
> > Technical Lead
> > Common Query Runtime/XML Query Processing
> > WebData XML Team
> > Microsoft
> >
Received on Friday, 30 May 2003 10:42:03 GMT

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